Analysis of Aroclor and Organochlorine Pesticides in Ground Water using Triple Quadrupole GC-MS/MS

Significance of Topic

Polychlorinated biphenyls and organochlorine pesticides are persistent organic pollutants regulated by environmental agencies due to their toxicity, persistence, and bioaccumulation. Conventional GC-ECD protocols rely on dual-column confirmation and visual pattern recognition to distinguish Aroclor mixtures, which is time-consuming and prone to interference.

Study Objectives and Overview

The study evaluates a triple quadrupole GC-MS/MS method for simultaneous determination of Aroclor mixtures and organochlorine pesticides in groundwater and wastewater. Objectives include comparing performance with EPA Method 608, simplifying data acquisition, and implementing a mathematical approach for Aroclor identification based on congener ratios.

Methodology and Instrumentation

Sample Preparation:

• Spike river water and effluent at 10 and 100 ng/L with Aroclor 1232, toxaphene, and pesticide standards.
• Adjust pH to 2, extract with methylene chloride, dry over sodium sulfate, re-extract at pH 11, and concentrate to 1 mL at 4 C.
• Add internal standards pyrene-d10 and decachlorobiphenyl at 100 ng/mL before analysis.

Instrumentation Used:

• GCMS-TQ8040 triple quadrupole system with AOC-20i+s autosampler.
• SH-Rxi-5MS column, 30 m × 0.25 mm, 0.25 μm film.
• Injection: 2 μL splitless at 275 C; oven program from 60 C to 330 C in four ramps.
• MS/MS: Electron ionization at 70 eV; interface 290 C; source 230 C; MRM acquisition, unit resolution, 0.5 s loop time.

Main Results and Discussion

Calibration and Sensitivity:

• Linear range of 0.5–200 ng/mL for most analytes with RF %RSD < 30%.
• Distinct MRM transitions allowed clear separation of mono- to nona-chlorobiphenyl congeners.

Recovery and Accuracy:

• Pesticide recoveries between 70 and 120% at low ng/L levels, demonstrating minimal matrix effects.
• Aroclor 1232 correctly identified by similarity index based on nine congener ratios, without subjective pattern matching.
• Total PCB quantitation via summation of congeners yielded recoveries of 100 to 128%.

Benefits and Practical Applications of the Method

This GC-MS/MS approach removes the need for a second confirmation column and manual chromatogram matching. High selectivity of MRM eliminates co-eluting interferences, improving confidence in trace analysis. The unified single-run protocol enhances laboratory throughput for environmental monitoring of groundwater and wastewater.

Future Trends and Opportunities

Future developments may include integrating automated extraction systems, expanding congener libraries to cover emerging pollutants, and applying machine learning algorithms for automated Aroclor pattern recognition. Ambient ionization interfaces could further reduce sample preparation time.

Conclusion

The triple quadrupole GC-MS/MS method offers a robust, selective, and efficient solution for simultaneous analysis of Aroclor mixtures and organochlorine pesticides in water matrices. Mathematical congener ratio identification and MRM selectivity streamline workflows, enhance reliability, and increase analytical throughput.

References

• USEPA Method 608 Organochlorine Pesticides and PCBs
• ASTM International WK54549 New Test Method for Determination of Organochlorine Pesticides and PCB Congeners in Aqueous Solutions by GC-TQMS